Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e4
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Comparison of compressive strength between three different plates for mandibular angle fractures fixation Mariana C. Negreiros Lyrio, Marcelo Silva Monnazzi*, Marcio De Moraes, Eduardo Hochuli-Vieira, José Mauricio Nunes Reis, Valfrido Antonio Pereira-Filho Dental School of Araraquara, Department of Diagnosis and Oral and Maxillofacial Surgery, Universidade Estadual Paulista, Unesp, Rua Humaita, 1680, 2 andar, Araraquara, São Paulo Cep 14801-903, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 27 February 2013 Accepted 8 October 2013
The present study aims to compare three types of internal fixation for fractures of the mandibular angle. Mechanical testing was performed on replicas of polyurethane hemimandibles sectioned at the angle region to simulate a fracture and fixed with three different hardwares. Fixation devices enrolled on this survey included the grid plates with and without an intermediate bar and the method described by Champy and colleagues in 1978 and the sample consisted of 10 hemimandibles for each group. Vertical loadings were applied on each hemimandible and recorded after a vertical displacement of 3 and 5 mm. Statistical analysis was made by means of the variance analysis (ANOVA) and the Duncan test with a significance level of 5%. The Champy technique showed a statistically significant increased resistance when compared to the grid plates after vertical displacements of 3 and 5 mm. The results of this survey suggest that the Champy technique, when compared to the grid plate positioned at the middle of the mandibular bone (placement site selected for this study), is more resistant than the grid plate and that the inclusion or not of an intermediate bar to the grid plates does not improve its resistance after linear vertical loadings. Ó 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Bone plate Bite force Compressive strength Mandibular fracture
1. Introduction Several papers describe the mandibular angle as the site of higher incidence for mandibular fractures (Ogundare et al., 2003; Paza et al., 2008; Sauerbier et al., 2010; Höfer et al., 2012). Moreover, fractures on this location present the highest complication rates amongst all mandibular fractures, despite all the advancements on internal fixation (Passeri et al., 1993; Ellis and Sinn, 1993; Ellis, 1993, 1999; Ellis and Walker, 1994, 1996; Schierle et al., 2013; Feller et al., 2003; Vineeth et al., 2013). Although there are obvious differences related to surgical access, size and type of fixation devices, the basic goals for all fixation techniques are the same: early return to function and enough stability for adequate osseous repair (Wittenberg et al., 1997). In order to minimize the extent of surgery and failure of the monocortical systems, as well as to avoid extra-oral approaches, the grid plates have been developed for the application on maxillofacial
* Corresponding author. Rua Voluntarios da Patria, 2777, ap 1001, Araraquara, São Paulo, Brazil. Tel.: þ55 1697823532, þ55 16 33845822. E-mail addresses: [email protected], [email protected] (M. S. Monnazzi).
trauma and orthognathic surgery. Those plates can be easily applied for fractures of the mandibular angle through an intra-oral approach and percutaneous screw positioning or with the aid of the 90 screwdriver (Guimond et al., 2005; Hochuli-Vieira et al., 2011). Some studies have reported a low incidence of complications with the use of the grid plates on the mandibular angle fractures (Hochuli-Vieira et al., 2011). They have become an alternative to conventional internal fixation with the advantage of simultaneous adaptation of the inferior and superior borders of the mandible providing increased stability (Feledy et al., 2004; Guimond et al., 2005; Zix et al., 2007). 2. Material and methods Morphologically standardized replicas of a human dentate mandible made of rigid polyurethane (SYNBONE 8311- Malans e Switzerland) were sectioned in the midline and the left side was chosen for this assay. An oblique cut at the mandibular angle region was performed from the retromolar region, 3 mm posteriorly to the distal border of the second molar, to the gonial region of the inferior border of the mandibular angle, simulating the fracture. An acrylic splint (Dental Vipi Ltda., Pirassununga-SP, Brazil) was built based
1010-5182/$ e see front matter Ó 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcms.2013.10.005
Please cite this article in press as: Negreiros Lyrio MC, et al., Comparison of compressive strength between three different plates for mandibular angle fractures fixation, Journal of Cranio-Maxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.005
2
M.C. Negreiros Lyrio et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e4
on the first sectioned model reproducing the same site of fracture for all the other samples. Three different systems of fixation were tested (Bucoplan e Engimplam Indústria e Comércio de Materiais Dentários, Rio ClaroSP, Brazil): Group I: 10 straight 4-hole titanium bone plates (1 mm 25 mm 5.5 mm) and 40 monocortical titanium screws (6.0 mm); system 2.0 Group II: 10 grid 4-hole titanium bone plates (1 mm 20 mm 11.5 mm) and 40 monocortical titanium screws (6.0 mm); system 2.0 Group III: 10 grid 4-hole titanium bone plates with an intermediate vertical reinforcement bar (1 mm 20 mm 11.5 mm) and 40 monocortical titanium screws (6.0 mm); system 2.0 All fractured replicas were reduced anatomically and another acrylic splint was fabricated to customize plate positioning according to the methodology described by Asprino et al. (2006). For group I, the plates were positioned at the external oblique line according to the technique described by Champy et al. (Fig. 1A). For groups II and III (Fig. 1B and C, respectively), the plates were positioned at the intermediary portion of the angle, 10 mm above the basal portion of the synthetic mandible, approximately at the neutral zone of the mandibular angle, following the manufacturer placement suggestion. The horizontal long axe of the grid plate was placed perpendicular to the fracture line. Another group of intact hemimandibles (group IV e control) was also tested to evaluate the force needed to fracture the sample as well as to ascertain correct positioning of the specimen on the loading device. The compressive loading tests were executed on the electromechanical testing machine EMIC DL 2000 (São José dos PinhaisPR, Brazil) at 1.0 mm/min and a load cell of 5.0 kN. After correct adaptation and fixation on the testing machine, the samples were subjected to a vertical compressive loading, simulating bite forces at the region of the cuspid and first bicuspids. By means of the progressive application of force over the specimens, the compressive strength (N) and the displacement (mm) imposed by the testing machine were obtained. Two distinct moments of loading support were measured and recorded. The first after 3.0 mm and the second after 5.0 mm of vertical displacement. The end of the assessment was established at the 5.0 mm dislocation even in cases where the system failed before this end-point. The statistical analysis was employed to compare quantitatively the groups studied regarding the means of compressive strength (N) at the two previously described vertical displacement points. The one-way (ANOVA) variance analysis was used to compare the groups with a significance level of 5.0%. After verification of statistically significant differences, Duncan test (a ¼ 0.05) was used for the pairwise comparison among the experimental groups.
Table 1 Statistical analysis and results (ANOVA) among the groups at the 3 mm point of vertical displacement. Group Group Group Group Group
I II III IV
Mean
Standard deviation
p-value
149.10 23.77 30.50 364.22
48.86 2.96 6.33 101.82
0.05
Table 2 Final results according to the Duncan test (3 mm point). Sig ¼ significance. Group I II III IV Sig.
N 10 10 10 10 -
Homogenous
Subgroups
Averages
1
2 149.10
3
23.77 30.50 0.792
1.000
364.22 1.000
3. Results For the 3 mm loading point, the ANOVA analysis showed statistically significant difference among the studied groups (Table 1) with a higher compressive strength registered for group I (Table 2). Therefore, the presence of the intermediate vertical bar did not increase the compressive strength of the grid plates. The mean values and standard deviations of loading at the 5 mm point indicated the same statistical results as for the 3 mm point (Tables 3 and 4). Likewise, the reinforcement bar of the grid plates on group III showed no increase on compressive strength. 4. Discussion The concepts of stable internal fixation and non-rigid fixation have been widely discussed. The increased application of the loadsharing principles for the treatment of mandibular fractures has motivated the development of new types of fixation systems with plates and screws that are able to provide increased stability with a smaller size and number of implants. The three dimensional systems, which are basically two plates linked by a vertical bar, are considered stable and resistant to masticatory loads and, therefore, they exempt the patient from the intermaxillary fixation period (Wittenberg et al., 1997; Guimond et al., 2005). The combination of monocortical screws with the cuboidal or rectangular design of the plates deliver the three dimensional stability to the system, while the reconstruction and compression systems rely on the plate thickness for their stability. Biomechanical studies have already shown the stability of the three dimensional bone plates, however only a few clinical studies have been reported regarding its use on fractures of the mandibular angle
Fig. 1. A: The Champy fixation technique representing group I. B: The 4-hole grid plate representing group II. C: The 4-hole grid plate with the middle reinforcement vertical bar representing group III.
Please cite this article in press as: Negreiros Lyrio MC, et al., Comparison of compressive strength between three different plates for mandibular angle fractures fixation, Journal of Cranio-Maxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.005
M.C. Negreiros Lyrio et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e4 Table 3 Statistical analysis and results (ANOVA) among the groups at the 5 mm point of vertical displacement. Group Group Group Group Group
I II III IV
Mean
Standard deviation
p-value
216.90 36.28 46.22 627.83
76.28 5.22 9.66 113.97
0.05
Table 4 Final results according to the Duncan test (5 mm point). Sig ¼ significance. Group I II III IV Sig.
N 10 10 10 10 e
Homogenous
Subgroups
Averages
1
2 216.90
3
36.28 46.22 0.748
1.000
627.83 1.000
(Wittenberg et al., 1997; Feledy et al., 2004; Guimond et al., 2005; Zix et al., 2007; Vineeth et al., 2013). The choice of a linear section for mimicking the fracture was based on the fact that the both the Champy method and the grid plates are indicated for this type of fracture (Champy et al., 1975; Jain et al., 2010). Fractures with bone fragments on the mandibular base and comminuted do not offer interfragmentary stability, therefore, are not amenable for treatment with such fixation systems (Zix et al., 2007; Hochuli-Vieira et al., 2011; Vineeth et al., 2013). The first biomechanical assessment of the three dimensional bone plates was conducted by Farmand (1995). However, little information could be retrieved regarding the type of plates evaluated on pig mandibles. Our study showed less mechanical resistance for the grid plates when compared to the Champy method, differing from Farmand (1996) results. However, no torsional or lateral forces were tested on our study (vertical loading only), what would probably have improved the performance of the grid plates. Considering that failure of the system occurs when there is movement between the segments altering the anatomic reduction, the present research shows that the Champy system has an increased resistance to vertical loading when compared to the grid plates at the two moments analyzed. It was also observed that the addition of an intermediate vertical bar to the grid plate did not increase the resistance of the three dimensional system. These results are probably due to the selected placement of the grid plate, that was positioned at the middle of the mandible like Höfer et al. (2012) did in his study. Evaluating all the involved factors, the 3-D plates system were initially developed to be positioned following Champy’s technique (Farmand, 1996; Vineeth et al., 2013) with the position of one bar of the plate at the oblique external line; however Höfer et al. (2012) showed good results with the placement of this kind of plate at the middle of the mandible. Besides that there are more differences like the thickness, the length, bending forces and others, which are not the subject of this publication, but which will influence the stability and the applicability of a plate. Therefore the authors in this study are comparing not only two different plate shapes, but also two different location sites, and making this comparison the results are the one stated above. Relevant advantages of the grid plates are the avoidance of an extra-oral incision with its inherent complications, ease of adaptation of the plate without distortion or displacement of the fracture, simultaneous stabilization of both the superior and inferior
3
borders and reduction of the surgical time (Farmand, 1996; Feledy et al., 2004; Zix et al., 2007), especially for this three dimensional plate tested, which is smaller than many others, also reducing costs of the treatment. It is important to remember, nonetheless, that this system is only indicated in cases with sufficient interfragmentary stability, such as simple fractures (Wittenberg et al., 1997; Guimond et al., 2005). Clinical reports with a low incidence of complications have suggested that those plates are a valuable alternative for the treatment of mandibular fractures (Zix et al., 2007; Hochuli-Vieira et al., 2011). Such statement is also reasonable given the fact that forces necessary for failure of the system are higher than the immediate postoperative forces exerted by the patients (Murphy et al., 1997; Peterson et al., 2005). Moreover, there are several factors that act in vivo and are not evaluated on in vitro studies. 5. Conclusions Mechanical considerations that can be concluded from this research are that the Champy method is more resistant to vertical loading than the grid plates tested at the described position and that the addition of an intermediate vertical bar does not increase the resistance of the grid plate to the type of loading examined, probably due to the fact that the grid plates does not follow the mandible’s trajectory lines and therefore is unlikely to improve stability. The present report tested a smaller grid plate than many of the other similar systems tested and regardless of the unsatisfactory performance of this system, clinical reports have already shown promising results. Consequently, further studies with different types of loading forces should be conducted to assess the efficacy of the system. Ethical approval Not required. Funding FAPESP N 2010/15741-8. Conflict of interest statement All authors disclose any financial and personal relationships with other people or organizations that could inappropriately influence this work. References Asprino L, Consani S, de Moraes M: A comparative biomechanical evaluation of mandibular condyle fracture plating techniques. J Oral Maxillofac Surg 64: 452e456, 2006 Champy M, Wilk A, Schnebelen JM: Treatment of mandibular fractures by means of osteosynthesis without intermaxillary immobilization according to F.X. Michelet’s technic. Zahn Mund Kieferheilkd Zentralbl 63: 339e341, 1975 Ellis III E, Sinn DP: Treatment of mandibular angle fractures using two 2.4-mm dynamic compression plates. J Oral Maxillofac Surg 51: 969e973, 1993 Ellis III E, Walker L: Treatment of mandibular angle fractures using two noncompression miniplates. J Oral Maxillofac Surg 52: 1032e1036, 1994 Ellis III E, Walker LR: Treatment of mandibular angle fractures using one noncompression miniplate. J Oral Maxillofac Surg 54: 864e871, 1996 Ellis III E: Treatment methods for fractures of the mandibular angle. Int J Oral Maxillofac Surg 28: 243e252, 1999 Ellis III E: Treatment of mandibular angle fractures using the AO reconstruction plate. J Oral Maxillofac Surg 51: 250e254, 1993 Farmand M: Three-dimensional plate fixation of fractures and osteotomies. Facial Plast Surg Clin North Am 3: 39e56, 1995 Farmand M: Experiences with the 3-D miniplate osteosynthesis in mandibular fractures. Fortschr Kiefer Gesichtschir 41: 85e87, 1996 Feledy J, Caterson EJ, Steger S, Stal S, Hollier L: Treatment of mandibular angle fractures with a matrix miniplate: a preliminary report. Plast Reconstr Surg 114: 1711e1716, 2004
Please cite this article in press as: Negreiros Lyrio MC, et al., Comparison of compressive strength between three different plates for mandibular angle fractures fixation, Journal of Cranio-Maxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.005
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Feller K, Schneider M, Hawitschka M, Pfeifer G, Lauer G, Eckelt U: Analysis of complications in fractures of the mandibular angle e a study with finite element computation and evaluation of data of 277 patients. J Craniomaxillofac Surg 31: 290e295, 2003 Guimond C, Johnson JV, Marchena JM: Fixation of mandibular angle fractures with 2.0mm 3-dimensional curved angle strut plate. J Oral Maxillofac Surg 63: 209e 214, 2005 Hochuli-Vieira E, Ha TK, Pereira-Filho VA, Landes CA: Use of rectangular grid miniplates for fracture fixation at the mandibular angle. J Oral Maxillofac Surg 69: 1436e1441, 2011 Höfer SS, Ha L, Ballon A, Sader R, Landes C: Treatment of mandibular angle fractures e linea oblique plate versus grid plate. J Craniomaxillofac Surg 40: 807e811, 2012 Jain MK, Manjunath KS, Bhagwan BK, Shah DK: Comparison of 3-dimensional and standard miniplate fixation in the management of mandibular fractures. J Oral Maxillofac Surg 68: 1568e1572, 2010 Murphy MT, Haug RH, Barber JE: An in vitro comparison of the mechanical characteristics of three sagittal ramus osteotomy fixation techniques. J Oral Maxillofac Surg 55: 489e494, 1997 Ogundare BO, Bonnick A, Bayley N: Pattern of mandibular fractures in an urban major trauma center. J Oral Maxillofac Surg 61: 713e718, 2003
Passeri LA, Ellis III E, Sinn DP: Complications of nonrigid fixation of mandibular angle fractures. J Oral Maxillofac Surg 51: 382e384, 1993 Paza AO, Abuabara A, Passeri LA: Analysis of 115 mandibular angle fractures. J Oral Maxillofac Surg 66: 73e76, 2008 Peterson GP, Haug RH, Van Sickels J: A biomechanical evaluation of bilateral sagittal ramus osteotomy fixation techniques. J Oral Maxillofac Surg 63: 1317e1324, 2005 Sauerbier S, Kuenz J, Hauptmann S, Hoogendijk CF, Liebehenschel N, Schön R, et al: Clinical aspects of a 2.0-mm locking plate system for mandibular fracture surgery. J Craniomaxillofac Surg 38: 501e504, 2010 Schierle HP, Schmelzeisen R, Rahn B, Pytlik C: One or two plate fixation of mandibular angle fractures? J Craniomaxillofac Surg 25: 162e168, 2013 Vineeth K, Lalitha RM, Prasad K, Ranganath K, Shwetha V, Singh J: A comparative evaluation between single noncompression titanium miniplate and three dimensional titanium miniplate in treatment of mandibular angle fracture e a randomized prospective study. J Craniomaxillofac Surg 41: 103e109, 2013 Wittenberg JM, Mukherjee DP, Smith BR, Kruse RN: Biomechanical evaluation of new fixation devices for mandibular angle fractures. Int J Oral Maxillofac Surg 26: 68e73, 1997 Zix J, Lieger O, Iizuka T: Use of straight and curved 3-dimensional titanium miniplates for fracture fixation at the mandibular angle. J Oral Maxillofac Surg 65: 1758e1763, 2007
Please cite this article in press as: Negreiros Lyrio MC, et al., Comparison of compressive strength between three different plates for mandibular angle fractures fixation, Journal of Cranio-Maxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.005
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Comparison of compressive strength between three different plates for mandibular angle fractures fixation Mariana C. Negreiros Lyrio, Marcelo Silva Monnazzi*, Marcio De Moraes, Eduardo Hochuli-Vieira, José Mauricio Nunes Reis, Valfrido Antonio Pereira-Filho Dental School of Araraquara, Department of Diagnosis and Oral and Maxillofacial Surgery, Universidade Estadual Paulista, Unesp, Rua Humaita, 1680, 2 andar, Araraquara, São Paulo Cep 14801-903, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 27 February 2013 Accepted 8 October 2013
The present study aims to compare three types of internal fixation for fractures of the mandibular angle. Mechanical testing was performed on replicas of polyurethane hemimandibles sectioned at the angle region to simulate a fracture and fixed with three different hardwares. Fixation devices enrolled on this survey included the grid plates with and without an intermediate bar and the method described by Champy and colleagues in 1978 and the sample consisted of 10 hemimandibles for each group. Vertical loadings were applied on each hemimandible and recorded after a vertical displacement of 3 and 5 mm. Statistical analysis was made by means of the variance analysis (ANOVA) and the Duncan test with a significance level of 5%. The Champy technique showed a statistically significant increased resistance when compared to the grid plates after vertical displacements of 3 and 5 mm. The results of this survey suggest that the Champy technique, when compared to the grid plate positioned at the middle of the mandibular bone (placement site selected for this study), is more resistant than the grid plate and that the inclusion or not of an intermediate bar to the grid plates does not improve its resistance after linear vertical loadings. Ó 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Bone plate Bite force Compressive strength Mandibular fracture
1. Introduction Several papers describe the mandibular angle as the site of higher incidence for mandibular fractures (Ogundare et al., 2003; Paza et al., 2008; Sauerbier et al., 2010; Höfer et al., 2012). Moreover, fractures on this location present the highest complication rates amongst all mandibular fractures, despite all the advancements on internal fixation (Passeri et al., 1993; Ellis and Sinn, 1993; Ellis, 1993, 1999; Ellis and Walker, 1994, 1996; Schierle et al., 2013; Feller et al., 2003; Vineeth et al., 2013). Although there are obvious differences related to surgical access, size and type of fixation devices, the basic goals for all fixation techniques are the same: early return to function and enough stability for adequate osseous repair (Wittenberg et al., 1997). In order to minimize the extent of surgery and failure of the monocortical systems, as well as to avoid extra-oral approaches, the grid plates have been developed for the application on maxillofacial
* Corresponding author. Rua Voluntarios da Patria, 2777, ap 1001, Araraquara, São Paulo, Brazil. Tel.: þ55 1697823532, þ55 16 33845822. E-mail addresses: [email protected], [email protected] (M. S. Monnazzi).
trauma and orthognathic surgery. Those plates can be easily applied for fractures of the mandibular angle through an intra-oral approach and percutaneous screw positioning or with the aid of the 90 screwdriver (Guimond et al., 2005; Hochuli-Vieira et al., 2011). Some studies have reported a low incidence of complications with the use of the grid plates on the mandibular angle fractures (Hochuli-Vieira et al., 2011). They have become an alternative to conventional internal fixation with the advantage of simultaneous adaptation of the inferior and superior borders of the mandible providing increased stability (Feledy et al., 2004; Guimond et al., 2005; Zix et al., 2007). 2. Material and methods Morphologically standardized replicas of a human dentate mandible made of rigid polyurethane (SYNBONE 8311- Malans e Switzerland) were sectioned in the midline and the left side was chosen for this assay. An oblique cut at the mandibular angle region was performed from the retromolar region, 3 mm posteriorly to the distal border of the second molar, to the gonial region of the inferior border of the mandibular angle, simulating the fracture. An acrylic splint (Dental Vipi Ltda., Pirassununga-SP, Brazil) was built based
1010-5182/$ e see front matter Ó 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcms.2013.10.005
Please cite this article in press as: Negreiros Lyrio MC, et al., Comparison of compressive strength between three different plates for mandibular angle fractures fixation, Journal of Cranio-Maxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.005
2
M.C. Negreiros Lyrio et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e4
on the first sectioned model reproducing the same site of fracture for all the other samples. Three different systems of fixation were tested (Bucoplan e Engimplam Indústria e Comércio de Materiais Dentários, Rio ClaroSP, Brazil): Group I: 10 straight 4-hole titanium bone plates (1 mm 25 mm 5.5 mm) and 40 monocortical titanium screws (6.0 mm); system 2.0 Group II: 10 grid 4-hole titanium bone plates (1 mm 20 mm 11.5 mm) and 40 monocortical titanium screws (6.0 mm); system 2.0 Group III: 10 grid 4-hole titanium bone plates with an intermediate vertical reinforcement bar (1 mm 20 mm 11.5 mm) and 40 monocortical titanium screws (6.0 mm); system 2.0 All fractured replicas were reduced anatomically and another acrylic splint was fabricated to customize plate positioning according to the methodology described by Asprino et al. (2006). For group I, the plates were positioned at the external oblique line according to the technique described by Champy et al. (Fig. 1A). For groups II and III (Fig. 1B and C, respectively), the plates were positioned at the intermediary portion of the angle, 10 mm above the basal portion of the synthetic mandible, approximately at the neutral zone of the mandibular angle, following the manufacturer placement suggestion. The horizontal long axe of the grid plate was placed perpendicular to the fracture line. Another group of intact hemimandibles (group IV e control) was also tested to evaluate the force needed to fracture the sample as well as to ascertain correct positioning of the specimen on the loading device. The compressive loading tests were executed on the electromechanical testing machine EMIC DL 2000 (São José dos PinhaisPR, Brazil) at 1.0 mm/min and a load cell of 5.0 kN. After correct adaptation and fixation on the testing machine, the samples were subjected to a vertical compressive loading, simulating bite forces at the region of the cuspid and first bicuspids. By means of the progressive application of force over the specimens, the compressive strength (N) and the displacement (mm) imposed by the testing machine were obtained. Two distinct moments of loading support were measured and recorded. The first after 3.0 mm and the second after 5.0 mm of vertical displacement. The end of the assessment was established at the 5.0 mm dislocation even in cases where the system failed before this end-point. The statistical analysis was employed to compare quantitatively the groups studied regarding the means of compressive strength (N) at the two previously described vertical displacement points. The one-way (ANOVA) variance analysis was used to compare the groups with a significance level of 5.0%. After verification of statistically significant differences, Duncan test (a ¼ 0.05) was used for the pairwise comparison among the experimental groups.
Table 1 Statistical analysis and results (ANOVA) among the groups at the 3 mm point of vertical displacement. Group Group Group Group Group
I II III IV
Mean
Standard deviation
p-value
149.10 23.77 30.50 364.22
48.86 2.96 6.33 101.82
0.05
Table 2 Final results according to the Duncan test (3 mm point). Sig ¼ significance. Group I II III IV Sig.
N 10 10 10 10 -
Homogenous
Subgroups
Averages
1
2 149.10
3
23.77 30.50 0.792
1.000
364.22 1.000
3. Results For the 3 mm loading point, the ANOVA analysis showed statistically significant difference among the studied groups (Table 1) with a higher compressive strength registered for group I (Table 2). Therefore, the presence of the intermediate vertical bar did not increase the compressive strength of the grid plates. The mean values and standard deviations of loading at the 5 mm point indicated the same statistical results as for the 3 mm point (Tables 3 and 4). Likewise, the reinforcement bar of the grid plates on group III showed no increase on compressive strength. 4. Discussion The concepts of stable internal fixation and non-rigid fixation have been widely discussed. The increased application of the loadsharing principles for the treatment of mandibular fractures has motivated the development of new types of fixation systems with plates and screws that are able to provide increased stability with a smaller size and number of implants. The three dimensional systems, which are basically two plates linked by a vertical bar, are considered stable and resistant to masticatory loads and, therefore, they exempt the patient from the intermaxillary fixation period (Wittenberg et al., 1997; Guimond et al., 2005). The combination of monocortical screws with the cuboidal or rectangular design of the plates deliver the three dimensional stability to the system, while the reconstruction and compression systems rely on the plate thickness for their stability. Biomechanical studies have already shown the stability of the three dimensional bone plates, however only a few clinical studies have been reported regarding its use on fractures of the mandibular angle
Fig. 1. A: The Champy fixation technique representing group I. B: The 4-hole grid plate representing group II. C: The 4-hole grid plate with the middle reinforcement vertical bar representing group III.
Please cite this article in press as: Negreiros Lyrio MC, et al., Comparison of compressive strength between three different plates for mandibular angle fractures fixation, Journal of Cranio-Maxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.005
M.C. Negreiros Lyrio et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e4 Table 3 Statistical analysis and results (ANOVA) among the groups at the 5 mm point of vertical displacement. Group Group Group Group Group
I II III IV
Mean
Standard deviation
p-value
216.90 36.28 46.22 627.83
76.28 5.22 9.66 113.97
0.05
Table 4 Final results according to the Duncan test (5 mm point). Sig ¼ significance. Group I II III IV Sig.
N 10 10 10 10 e
Homogenous
Subgroups
Averages
1
2 216.90
3
36.28 46.22 0.748
1.000
627.83 1.000
(Wittenberg et al., 1997; Feledy et al., 2004; Guimond et al., 2005; Zix et al., 2007; Vineeth et al., 2013). The choice of a linear section for mimicking the fracture was based on the fact that the both the Champy method and the grid plates are indicated for this type of fracture (Champy et al., 1975; Jain et al., 2010). Fractures with bone fragments on the mandibular base and comminuted do not offer interfragmentary stability, therefore, are not amenable for treatment with such fixation systems (Zix et al., 2007; Hochuli-Vieira et al., 2011; Vineeth et al., 2013). The first biomechanical assessment of the three dimensional bone plates was conducted by Farmand (1995). However, little information could be retrieved regarding the type of plates evaluated on pig mandibles. Our study showed less mechanical resistance for the grid plates when compared to the Champy method, differing from Farmand (1996) results. However, no torsional or lateral forces were tested on our study (vertical loading only), what would probably have improved the performance of the grid plates. Considering that failure of the system occurs when there is movement between the segments altering the anatomic reduction, the present research shows that the Champy system has an increased resistance to vertical loading when compared to the grid plates at the two moments analyzed. It was also observed that the addition of an intermediate vertical bar to the grid plate did not increase the resistance of the three dimensional system. These results are probably due to the selected placement of the grid plate, that was positioned at the middle of the mandible like Höfer et al. (2012) did in his study. Evaluating all the involved factors, the 3-D plates system were initially developed to be positioned following Champy’s technique (Farmand, 1996; Vineeth et al., 2013) with the position of one bar of the plate at the oblique external line; however Höfer et al. (2012) showed good results with the placement of this kind of plate at the middle of the mandible. Besides that there are more differences like the thickness, the length, bending forces and others, which are not the subject of this publication, but which will influence the stability and the applicability of a plate. Therefore the authors in this study are comparing not only two different plate shapes, but also two different location sites, and making this comparison the results are the one stated above. Relevant advantages of the grid plates are the avoidance of an extra-oral incision with its inherent complications, ease of adaptation of the plate without distortion or displacement of the fracture, simultaneous stabilization of both the superior and inferior
3
borders and reduction of the surgical time (Farmand, 1996; Feledy et al., 2004; Zix et al., 2007), especially for this three dimensional plate tested, which is smaller than many others, also reducing costs of the treatment. It is important to remember, nonetheless, that this system is only indicated in cases with sufficient interfragmentary stability, such as simple fractures (Wittenberg et al., 1997; Guimond et al., 2005). Clinical reports with a low incidence of complications have suggested that those plates are a valuable alternative for the treatment of mandibular fractures (Zix et al., 2007; Hochuli-Vieira et al., 2011). Such statement is also reasonable given the fact that forces necessary for failure of the system are higher than the immediate postoperative forces exerted by the patients (Murphy et al., 1997; Peterson et al., 2005). Moreover, there are several factors that act in vivo and are not evaluated on in vitro studies. 5. Conclusions Mechanical considerations that can be concluded from this research are that the Champy method is more resistant to vertical loading than the grid plates tested at the described position and that the addition of an intermediate vertical bar does not increase the resistance of the grid plate to the type of loading examined, probably due to the fact that the grid plates does not follow the mandible’s trajectory lines and therefore is unlikely to improve stability. The present report tested a smaller grid plate than many of the other similar systems tested and regardless of the unsatisfactory performance of this system, clinical reports have already shown promising results. Consequently, further studies with different types of loading forces should be conducted to assess the efficacy of the system. Ethical approval Not required. Funding FAPESP N 2010/15741-8. Conflict of interest statement All authors disclose any financial and personal relationships with other people or organizations that could inappropriately influence this work. References Asprino L, Consani S, de Moraes M: A comparative biomechanical evaluation of mandibular condyle fracture plating techniques. J Oral Maxillofac Surg 64: 452e456, 2006 Champy M, Wilk A, Schnebelen JM: Treatment of mandibular fractures by means of osteosynthesis without intermaxillary immobilization according to F.X. Michelet’s technic. Zahn Mund Kieferheilkd Zentralbl 63: 339e341, 1975 Ellis III E, Sinn DP: Treatment of mandibular angle fractures using two 2.4-mm dynamic compression plates. J Oral Maxillofac Surg 51: 969e973, 1993 Ellis III E, Walker L: Treatment of mandibular angle fractures using two noncompression miniplates. J Oral Maxillofac Surg 52: 1032e1036, 1994 Ellis III E, Walker LR: Treatment of mandibular angle fractures using one noncompression miniplate. J Oral Maxillofac Surg 54: 864e871, 1996 Ellis III E: Treatment methods for fractures of the mandibular angle. Int J Oral Maxillofac Surg 28: 243e252, 1999 Ellis III E: Treatment of mandibular angle fractures using the AO reconstruction plate. J Oral Maxillofac Surg 51: 250e254, 1993 Farmand M: Three-dimensional plate fixation of fractures and osteotomies. Facial Plast Surg Clin North Am 3: 39e56, 1995 Farmand M: Experiences with the 3-D miniplate osteosynthesis in mandibular fractures. Fortschr Kiefer Gesichtschir 41: 85e87, 1996 Feledy J, Caterson EJ, Steger S, Stal S, Hollier L: Treatment of mandibular angle fractures with a matrix miniplate: a preliminary report. Plast Reconstr Surg 114: 1711e1716, 2004
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